This invention relates to pharmaceutically active compounds which are useful for the treatment of bacterial infections.
There is a medical need for novel antibiotics and a market opportunity for new antibacterial agents. Thus, the object of this invention is to identify novel compounds having antibiotic activity.
While the overall pathway of saturated fatty acid biosynthesis is similar in all organisms, the fatty acid synthase (FAS) systems vary considerably with respect to their structural organization. Vertebrates and yeast possess a FAS in which all the enzymatic activities are encoded on one or two polypeptide chains, respectively, and the acyl carrier protein (ACP) is an integral part of the complex. In contrast, in bacterial FAS, each of the reactions is catalyzed by a distinct, mono-functional enzyme and the ACP is a discrete protein. Therefore, there is considerable potential for the selective inhibition of the bacterial system by antibacterial agents.
Fab I (previously designated EnvM) functions as an enoyl-ACP reductase (Bergler, et al, (1994), J. Biol. Chem. 269, 5493-5496) in the final step of the four reactions involved in each cycle of bacterial fatty acid biosynthesis. In this pathway, the first step is catalyzed by xcex2-ketoacyl-ACP synthase, which condenses malonyl-ACP with acetyl-CoA (FabH, synthase III). In subsequent rounds, malonyl-ACP is condensed with the growing-chain acyl-ACP (FabB and FabF, synthases I and II, respectively). The second step in the elongation cycle is ketoester reduction by NADPH-dependent xcex2-ketoacyl-ACP reductase (FabG). Subsequent dehydration by xcex2-hydroxyacyl-ACP dehydrase (either FabA or FabZ) leads to trans-2-enoyl-ACP, which in turn is converted to acyl-ACP by NADH-dependent enoyl-ACP reductase (Fab I). Further rounds of this cycle, adding two carbon atoms per cycle, eventually lead to palmitoyl-ACP (16C), where upon the cycle is stopped largely due to feedback inhibition of Fab I by palmitoyl-ACP (Heath, et al, (1996), J. Biol. Chem. 271, 1833-1836). Thus, Fab I is a major biosynthetic enzyme and is a key regulatory point in the overall synthetic pathway of bacterial fatty acid biosynthesis. Therefore, Fab I is an ideal target for antibacterial intervention.
Studies have shown that diazaborine antibiotics inhibit fatty acid, phospholipid and lipopolysaccharide (LPS) biosynthesis and that the antibacterial target of these compounds is Fab I. For example, derivative 2b18 from Grassberger, et al (1984) J. Med Chem 27 947-953 has been reported to be a non-competitive inhibitor of Fab I (Bergler, et al, (1994), J. Biol. Chem. 269, 5493-5496). Also, plasmids containing the Fab I gene from diazaborine resistant S. typhimurium conferred diazaborine resistance in E. coli (Turnowsky, et al, (1989), J. Bacteriol., 171, 6555-6565). Furthermore, inhibition of Fab I either by diazaborine or by raising the temperature in a Fab I temperature sensitive mutant is lethal. These results demonstrate that Fab I is essential to the survival of the organism (Bergler, et al, (1994), J. Biol. Chem. 269, 5493-5496).
Recent studies have shown that Fab I is also the target for the broad spectrum antibacterial agent triclosan (McMurry, et al, (1998) Nature 394, 531-532). A crystal structure of the E. Coli Fab I complexed with AND and triclosan shows that triclosan acts as a site-directed, very potent inhibitor of Fab I by mimicking its natural substrate (Levy, et al, (1999) Nature 398, 383-384). Ward, et al ((1999) Biochem. 38, 12514-12525) have shown that there is no evidence for the formation of a covalent complex between Fab I and triclosan, which would be analogous to the diazaborines; triclosan differs from these compounds in that it is a reversible inhibitor of Fab I. The structural data for the complex of Fab I with NAD and triclosan provides important information about Fab I as a therapeutic target.
Importantly, it has now been discovered that certain compounds have antibacterial activity and some of these antibacterial compounds are Fab I inhibitors. Therefore, the compounds of the present invention may be useful for the treatment of bacterial infections in mammals, particularly in man.
This invention comprises compounds of formula (I) and formula (II), as described hereinafter, which are useful in the treatment of bacterial infections.
This invention is also a pharmaceutical composition comprising a compound according to formula (I) or formula (II) and a pharmaceutically acceptable carrier.
This invention is also a method of treating bacterial infections by inhibiting Fab I. In a particular aspect, the compounds of this invention are useful as antibacterial agents.
This invention comprises compounds of formula (I) or formula (II): 
wherein:
R1 is C1-4alkyl, Ar or 2-thienyl or 3-thienyl;
R2 is C1-4alkyl or Ar; and
n is 0-3;
or a pharmaceutically acceptable salt thereof.
Also included in this invention are pharmaceutically acceptable addition salts and complexes of the compounds of this invention. In cases wherein the compounds of this invention may have one or more chiral centers, unless specified, this invention includes each unique racemic compound, as well as each unique nonracemic compound. These compounds may be synthesized and resolved by conventional techniques.
In cases in which compounds have unsaturated carbonxe2x80x94carbon double bonds, both the cis (Z) and trans (E) isomers are within the scope of this invention. In cases wherein compounds may exist in tautomeric forms, such as keto-enol tautomers, such as 
and 
each tautomeric form is contemplated as being included within this invention, whether existing in equilibrium or locked in one form by appropriate substitution with Rxe2x80x2. The meaning of any substituent at any one occurrence is independent of its meaning, or any other substituent""s meaning, at any other occurrence.
Also included in this invention are prodrugs of the compounds of this invention. Prodrugs are considered to be any covalently bonded carriers which release the active parent drug according to formula (I) or in formula (II) in vivo.
The compounds of formula (I) and formula (II) may be useful in the treatment of bacterial infections. Also, the compounds of this invention may be useful as antifungal agents. Additionally, the compounds may be useful in combination with known antibiotics.
Preferably, the compounds of the invention comprise compounds of the formula (I): 
wherein:
R1 is C1-4alkyl, Ar or 2-thienyl or 3-thienyl;
R2 is C1-4alkyl or Ar; and
n is 0-3;
or a pharmaceutically acceptable salt thereof.
With respect to formula (I):
Suitably, R2 is Ar. Preferably, R2 is phenyl, unsubstituted or substituted by one or two substituents selected from the group consisting of C1-4alkyl, C1-4alkoxy, C1-4alkoxy, CF3, F, Cl, Br and I, or methylenedioxy. Preferably, n is 1
Suitably, R1 is Ar or Het. Preferably, R1 is 2- or 3-thienyl or phenyl, unsubstituted or substituted by one or two substituents selected from the group consisting of C1-4alkyl, C1-4alkoxy, CF3, F, Cl, Br and I.
Alternately, the compounds of the invention comprise compounds of the formula (II): 
wherein:
R1 is C1-4alkyl, Ar or 2-thienyl or 3-thienyl;
R2 is C1-4alkyl or Ar; and
n is 0-3;
or a pharmaceutically acceptable salt thereof.
With respect to formula (II):
Suitably, R2 is Ar. Preferably, R2 is phenyl, unsubstituted or substituted by one or two substituents selected from the group consisting of C1-4alkyl, C1-4alkoxy, CF3, F, Cl, Br, I and phenyl, or methylenedioxy. Preferably, n is 1
Suitably, R1 is Ar. Preferably, R1 is phenyl or naphthyl, unsubstituted or substituted by one or two substituents selected from the group consisting of C1-4alkyl, C1-4alkoxy, CF3, F, Cl, Br, I and phenyl.
Representative of the novel compounds of this invention are the compounds named in Examples 1-91.
Representative of the antibacterial compounds having Fab I inhibitory activity are the following:
1-Benzyl-4-(2-thienyl)-1H-imidazole;
1-Benzyl-4-(3-thienyl)-1H-imidazole;
1-Benzyl-4-(4-methoxyphenyl)-1H-imidazole;
1-(4-Methylbenzyl)-4-(3-thienyl)-1H-imidazole;
4-(4-Methoxyphenyl)-1-(4-methylbenzyl)-1H-imidazole:
1-(4-Chlorobenzyl)-4-(2-thienyl)-1H-imidazole;
1-(4-Chlorobenzyl)-4-(3-thienyl)-1H-imidazole;
1-(4-Chlorobenzyl)-4-(4-methoxyphenyl)-1H-imidazole;
1-(3,4-Dichlorobenzyl)-4-(2-thienyl)-1H-imidazole;
1-(3,4-Dichlorobenzyl)-4-[4-(trifluoromethyl)phenyl]-1H-imidazole;
1-(3,4-Dichlorobenzyl)-4-phenyl-1H-imidazole;
1-(4-Methoxybenzyl)-4-(3-thienyl)-1H-imidazole;
1-(4-Methoxybenzyl)-4-(4-methoxyphenyl)-1H-imidazole;
1-Benzo[1,3]dioxol-5-ylmethyl-4-thiophen-3-yl-1H-imidazole;
4-(2-Methoxy-phenyl)-1-naphthalen-2-ylmethyl-1H-imidazole;
1-(2,4-Dichloro-benzyl)-4-thiophen-3-yl-1H-imidazole;
4-Thiophen-3-yl-1-(3-m-tolyl-propyl)-1H-imidazole;
1-[3-(4-Methoxy-phenyl)-propyl]-4-thiophen-3-yl-1H-imidazole;
4-Thiophen-3-yl-1-[3-(3-trifluoromethyl-phenyl)-propyl]-1H-imidazole;
1-(4-Isopropyl-benzyl)-4-thiophen-3-yl-1H-imidazole;
1-[3-(3-Methoxy-phenyl)-propyl]-4-thiophen-3-yl-1H-imidazole;
1-(4-Ethyl-benzyl)-4-thiophen-3-yl-1H-imidazole;
1-(4-Methylbenzyl)-4-phenyl-1H-imidazole; or
1-(4-Methylbenzyl)-4-(2-thienyl)-1H-imidazole;
or a pharmaceutically acceptable salt thereof.
Abbreviations and symbols commonly used in the peptide and chemical arts are used herein to describe the compounds of this invention.
C1-4alkyl as applied herein means an optionally substituted alkyl group of 1 to 4 carbon atoms, and includes methyl, ethyl, n-propyl, isopropyl, n-butyl, isobutyl and t-butyl. Any C1-4alkyl may be optionally substituted with the group Rx, which may be on any carbon atom that results in a stable structure and is available by conventional synthetic techniques. Suitable groups for Rx are C1-4alkyl, C1-4alkoxy, CF3, F, Cl, Br, I or N(Rxe2x80x2)2, in which each Rxe2x80x2 independently is H, C1-C4alkyl or Ar-C0-6alkyl.
C1-4alkoxy as applied herein means an alkyl group of 1 to 4 carbon atoms attached to an oxygen atom. C1-4alkoxy includes methoxy, ethoxy, propoxy and butyloxy.
Halogen or halo means F, Cl, Br, and I.
Ar, or aryl, as applied herein, means phenyl or naphthyl, or phenyl or naphthyl substituted by one to three substituents, such as C1-4alkyl, C1-4alkoxy, CF3, F, Cl, Br, I or phenyl, or methylenedioxy, that are available by chemical synthesis and are stable are within the scope of this invention.
Certain radical groups are abbreviated herein. t-Bu refers to the tertiary butyl radical, Ph refers to the phenyl radical, Bn refers to the benzyl radical, Me refers to methyl, Et refers to ethyl, Ac refers to acetyl, Alk refers to C1-4alkyl, Nph refers to 1- or 2-naphthyl and cHex refers to cyclohexyl.
The compounds of formula (I) are generally prepared by the following processes:
(i) heating a compound of formula (III) with a compound of formula (IV): 
wherein R1, R2 and n are as defined in formula (I), with any reactive functional groups protected; or
(ii) reacting a compound of formula (IV) with a compound of formula (V): 
wherein R1, R2 and n are as defined in formula (1) and Y is halo, methanesulfonyl, toluenesulfonyl, or trifluoromethanesulfonate, with any reactive functional groups protected, in the presence of a base in an aprotic solvent; or
(ii) reacting a compound of formula (VI) with a compound of formula (VII): 
wherein R1, R2 and n are as defined in formula (I), with any reactive functional groups protected, in the presence of glyoxylic acid and a base;
and thereafter removing any protecting groups, and optionally forming a pharmaceutically acceptable salt.
The compounds of formula (II) are generally prepared by reacting a compound of formula (VIII) with a compound of formula (IX): 
wherein R1, R2 and n are as defined in formula (II), with any reactive functional groups protected;
and thereafter removing any protecting groups, and optionally forming a pharmaceutically acceptable salt.
Compounds of the formula (I) are prepared by the general methods described in Scheme 1. 
Compounds of formula (I) are prepared by methods analogous to those shown in Scheme 1. Alkyl or aryl aldehydes, such as the 1-Scheme 1 compound, are condensed with tosylmethylisocyanide in a dipolar cycloaddition catalyzed by sodium cyanide to give oxazolines, such as the 3-Scheme 1 compound. The oxazolines, for example the 3-Scheme 1 compound, are then heated with primary amines, such as 4-methylbenzylamine, to give the imidazoles of formula (I), such as the 4-Scheme 1 compound.
Alternatively, compounds of formula (I) are generally prepared as described in Scheme 2. 
Compounds of formula (I) are prepared by methods analogous to those shown in Scheme 2. 4-Iodo-1H-imidazole, prepared according to Cliff and Pyne (Synthesis, 1994, 681-682) is condensed with a suitable organo-boronic acid, such as 2-Scheme 2, under Suzuki coupling conditions to give the corresponding substituted imidazole, 3-Scheme 2. Typical Suzuki conditions use a catalytic amount of a Pd(0) catalysts, such as tetrakistriphenylphosphine palladium, and an excess of a base, such as sodium carbonate, in a polar solvent, such as dimethoxyethane and water. The substituted imidazole is then alkylated with an alkyl halide, such as 4-methoxybenzyl bromide, in the presence of a base, such as potasium carbonate, in a polar aprotic solvent, such as DMF to give an imidazole of formula (I), such as 4-Scheme 2. Other suitable alkylating agents include alkyl mesylates, alkyl tosylates and alkyl triflates.
Alternatively, compounds of formula (I) are generally prepared as described in Scheme 3. 
Compounds of formula (I) are prepared by methods analogous to those shown in Scheme 3. A primary amine, such as 1-Scheme 3, is condensed with an aryl substituted tosyl methyl isocyanates, such as 2-Scheme 3, in the presence of glyoxylic acid and a base, such as K2CO3, to give a compound of formula (I), such as 3-Scheme 3. The substituted tosyl methyl isocyanate. 2-Scheme 3, is prepared according to Sisko, Mellinger, Sheldrake and Baine (Tetrahedron Letters, 1996, 37(45), 8113-8116).
Compounds of the formula (II) are prepared by the general methods described in Scheme 4. 
Compounds of formula (II) are prepared by methods analogous to those shown in Scheme 4. Aryl or alkyl nitriles, such as the 1-Scheme 4 compound, are converted to the corresponding amidine, such as the 2-Scheme 4 compound, via the corresponding imidate. The amidines are condensed with suitable alpha halo ketones, such as the 3-Scheme 4 compound, to give compounds of formula (II), such as the 4-Scheme 4 compound.
The formula (I) and formula (II) compounds of the present invention may also be prepared by methods known to those skilled in the art. For example, compounds of formula (I) may be synthesized according to the method of Home, D. A.; Yakushijin, K.; Bxc3xcchi, G. Heterocycles, 1994, 39, 139-153 and compounds of formula (II) may be synthesized according to the method of Caroon, J. M.; Clark, R. D.; Kluge, A. F.; Olah, R.; Repke, D. B.; Unger, S. H.; Michel, A. D.; Whiting, R. L. J. Med. Chem., 1982, 25(6), 666-670. Reference should be made to said articles for their full disclosure, particularly to the methods of preparing the compounds described therein, said disclosures being incorporated herein by reference.
Acid addition salts of the compounds of the invention are prepared in a standard manner in a suitable solvent from the parent compound and an excess of an acid, such as hydrochloric, hydrobromic, hydrofluoric, sulfuric, phosphoric, acetic, trifluoroacetic, maleic, succinic or methanesulfonic. Certain of the compounds form inner salts or zwitterions which may be acceptable. Cationic salts are prepared by treating the parent compound with an excess of an alkaline reagent, such as a hydroxide, carbonate or alkoxide, containing the appropriate cation; or with an appropriate organic amine. Cations such as Li+, Na+, K+, Ca++, Mg++ and NH4+ are specific examples of cations present in pharmaceutically acceptable salts.
This invention also provides a pharmaceutical composition which comprises a compound according to formula (I) or formula (II) and a pharmaceutically acceptable carrier. Accordingly, the compounds of formula (I) and formula (II) may be used in the manufacture of a medicament. Pharmaceutical compositions of the compounds of formula (I) and formula (II) prepared as hereinbefore described may be formulated as solutions or lyophilized powders for parenteral administration. Powders may be reconstituted by addition of a suitable diluent or other pharmaceutically acceptable carrier prior to use. The liquid formulation may be a buffered, isotonic, aqueous solution. Examples of suitable diluents are normal isotonic saline solution, standard 5% dextrose in water or buffered sodium or ammonium acetate solution. Such formulation is especially suitable for parenteral administration, but may also be used for oral administration or contained in a metered dose inhaler or nebulizer for insufflation. It may be desirable to add excipients such as polyvinylpyrrolidone, gelatin, hydroxy cellulose, acacia, polyethylene glycol, mannitol, sodium chloride or sodium citrate.
Alternately, these compounds may be encapsulated, tableted or prepared in a emulsion or syrup for oral administration. Pharmaceutically acceptable solid or liquid carriers may be added to enhance or stabilize the composition, or to facilitate preparation of the composition. Solid carriers include starch, lactose, calcium sulfate dihydrate, terra alba, magnesium stearate or stearic acid, talc, pectin, acacia, agar or gelatin. Liquid carriers include syrup, peanut oil, olive oil, saline and water. The carrier may also include a sustained release material such as glyceryl monostearate or glyceryl distearate, alone or with a wax. The amount of solid carrier varies but, preferably, will be between about 20 mg to about 1 g per dosage unit. The pharmaceutical preparations are made following the conventional techniques of pharmacy involving milling, mixing, granulating, and compressing, when necessary, for tablet forms; or milling, mixing and filling for hard gelatin capsule forms. When a liquid carrier is used, the preparation will be in the form of a syrup, elixir, emulsion or an aqueous or non-aqueous suspension. Such a liquid formulation may be administered directly p.o. or filled into a soft gelatin capsule.
For rectal administration, the compounds of this invention may also be combined with excipients, such as cocoa butter, glycerin, gelatin or polyethylene glycols, and molded into a suppository.
For topical administration, the compounds of this invention may be combined with diluents to take the form of ointments, gels, pastes, creams, powders or sprays. The compositions which are ointments, gels, pastes or creams contain diluents, for example, animal and vegetable fats, waxes, paraffins, starch, tragacanth, cellulose derivatives, polyethylene glycols, silicones, bentonites, silicic acid, talc and zinc oxide, or mixtures of these substances. The compositions which are powders or sprays contain diluents, for example, lactose, talc, silicic acid, aluminum hydroxide, calcium silicate and polyamide powder, or mixtures of these substances. Additionally, for topical ophthalmologic administration, the typical carriers are water, mixtures of water and water miscible solvents, such as lower alkanols or vegetable oils, and water-soluble non-toxic polymers, for example cellulose derivatives, such as methyl cellulose.
The compounds described herein are useful for treating bacterial infections. Also, certain compounds of this invention are Fab I inhibitors. For instance, these compounds are useful for the treatment of bacterial infections, such as, for example, infections of upper respiratory tract (e.g. otitis media, bacterial tracheitis, acute epiglottitis, thyroiditis), lower respiratory (e.g. empyema, lung abscess), cardiac (e.g. infective endocarditis), gastrointestinal (e.g. secretory diarrhoea, splenic abscess, retroperitoneal abscess), CNS (e.g. cerebral abscess), eye (e.g. blepharitis, conjunctivitis, keratitis, endophthalmitis, preseptal and orbital cellulitis, darcryocystitis), kidney and urinary tract (e.g. epididymitis, intrarenal and perinephric abscess, toxic shock syndrome), skin (e.g. impetigo, folliculitis, cutaneous abscesses, cellulitis, wound infection, bacterial myositis), and bone and joint (e.g. septic arthritis, osteomyelitis). Also, the compounds of this invention may be useful as antifungal agents.
The compounds of this invention are administered to the patient, in a manner such that the concentration of drug is sufficient to treat bacterial infections. The pharmaceutical composition containing the compound is administered at an oral dose of between about 10 mg to about 1000 mg, taken once or several times daily, in a manner consistent with the condition of the patient. Preferably, the oral dose would be about 50 mg to about 500 mg, although the dose may be varied depending upon the age, body weight and symptoms of the patient. For acute therapy, parenteral administration is preferred. An intravenous infusion of the compound of formula (I) in 5% dextrose in water or normal saline, or a similar formulation with suitable excipients, is most effective, although an intramuscular bolus injection is also useful. The precise level and method by which the compounds are administered is readily determined by one skilled in the art.
The compounds may be tested in one of several biological assays to determine the concentration of compound which is required to have a given pharmacological effect.
Cloning of S. aureus FabI:
The fabI gene was cloned from the chromosomal DNA of S. auretis strain WCUH29 using the polymerase chain reaction. Amplification was performed using Taq DNA polymerase (BRL) and the following primers: 5xe2x80x2-CGCCTCGAGATGTTAAATCTTGAAAACAAAACATATGTC-3xe2x80x2 and 5xe2x80x2-CGCGGATCCAATCAAGTCAGGTTGAAATATCCA-3xe2x80x2 (XhoI and BamHI sites underlined). The resulting fragment was then digested with XhoI and BamHI and ligated into XhoI- and BamHI-digested expression vector pET-16b (Novagen), producing pET-His10-fabI. The gene sequence of fabI was confirmed by automated cycle sequencing using an Applied Biosystems model 377 machine. The untagged version of pET-FabI was constructed by digesting pET-His10-fabI with NcoI and NdeI to remove a 97 bp fragment encoding the His 10 tag, the factor Xa cleavage site and the first 8 amino acids of FabI, and replacing it with a linker encoding the first 8 amino acids of FabI plus a glycine residue between the initiator methionine and the lysine at position 2. This plasmid was called pET-fabI. The linker was made by annealing the following two oligonucleotides: 5xe2x80x2-CATGGGCTTAAATCTTGAAAACAAAACA-3xe2x80x2 and 5xe2x80x2-TATGTTTTGTTTTCAAGATTTAAGCC-3xe2x80x2. The linker sequence in pET-fabI was confirmed by dideoxy sequencing. Only native FabI was used for compound evaluation. For overproduction of native FabI, plasmid pET-fabI was transformed into BL21(DE3) (Novagen) cells, to form strain BL21(DE3):pET-fabI.
Purification of S. aureus FabI
S. aureus FabI was expressed as soluble protein to 10% of total cell protein, 400 g cells being recovered from 15L fermentation in tryptone phosphate medium. The cells were lysed and the sample centrifuged. The resulting supernatant was filtered and purified using three consecutive chromatography columns: ion-exchange (Sourse 15Q), dye-affinity (Blue sepharose), and size exclusion chromatography columns (Superose 12). After each column the FabI containing fractions were pooled, concentrated, and checked for purity and biological activity.
Cloning of E. coli FabI:
A PCR fragment of correct size for E. coli FabI was PCR amplified from E. coli chromosomal DNA, subcloned into the TOPO TA cloning vector, and verified by colony PCR+restriction endonuclease analysis. The presumptive E. coli FabI PCR fragment was subcloned into the expression vector pBluePet. The FabI clone was transformed into E. coli strain BL21(DE3). Small Scale expression studies show an over-expressed protein band of correct molecular weight (xcx9c28 Kda) for E. coli FabI clearly visible following Coomassie staining of SDS PAGE gels. DNA sequencing of the E. coli FabI expression constructs illustrated that no errors were apparent. Nxe2x80x2 terminal amino acid sequencing has confirmed the over-expressed protein band to be E. coli FabI.
Purification of E. coli FabI
E. coli FabI was expressed as soluble protein to 15% of total cell protein, 120 g cells being recovered from 3L fermentation in shake flasks in modified terrific broth. The cells were lysed and the sample centrifuged. The resulting supernatant was filtered and purified using three consecutive chromatography columns: ion-exchange (Sourse 15Q), dye-affinity (blue sepharose), and size exclusion (superose 12). After each column the FabI containing fractions were pooled, concentrated and checked for purity and biological activity.
S aureus FabI Enzyme Inhibition Assay:
Assays were carried out in half-area, 96-well microtitre plates. Compounds were evaluated in 50-uL assay mixtures containing 100 mM NaADA, pH 6.5 (ADA=N-[2-acetamido]-2-iminodiacetic acid), 4% glycerol, 0.25 mM crotonoyl CoA, 1 mM NADH, and an appropriate dilution of S. aureus FabI. Inhibitors were typically varied over the range of 0.01-10 uM. The consumption of NADH was monitored for 20 minutes at 30xc2x0 C. by following the change in absorbance at 340 nm. Initial velocities were estimated from an exponential fit of the non-linear progress curves represented by the slope of the tangent at t=0 min. IC50""s were estimated from a fit of the initial velocities to a standard, 4-parameter model and are typically reported as the mean xc2x1S.D. of duplicate determinations. Triclosan, a commercial antibacterial agent and inhibitor of FabI, is currently included in all assays as a positive control.
E. coli FabI Enzyme Inhibition Assay:
Assays were carried out in half-area, 96-well microtitre plates. Compounds were evaluated in 150-uL assay mixtures containing 100 mM NaADA, pH 6.5 (ADA=N-[2-acetamido]-2-iminodiacetic acid), 4% glycerol, 0.25 mM crotonoyl CoA, 50 uM NADH, and an appropriate dilution of E. coli FabI. Inhibitors were typically varied over the range of 0.01-10 uM. The consumption of NADH was monitored for 20 minutes at 30xc2x0 C. by following the change in absorbance at 340 nm. Initial velocities were estimated from an exponential fit of the non-linear progress curves represented by the slope of the tangent at t=0 min. IC50""s were estimated from a fit of the initial velocities to a standard, 4-parameter model and are typically reported as the mean xc2x1S.D. of duplicate determinations. Triclosan, a commercial antibacterial agent and inhibitor of FabI, is currently included in all assays as a positive control.
Antimicrobial Activity Assay:
Whole-cell antimicrobial activity was determined by broth microdilution using the National Committee for Clinical Laboratory Standards (NCCLS) recommended procedure. Document M7-A4, xe2x80x9cMethods for Dilution Susceptibility Tests for Bacteria that Grow Aerobicallyxe2x80x9d. The compound was tested in serial two-fold dilutions ranging from 0.06 to 64 mcg/mL. A panel of 12 strains were evaluated in the assay. This panel consisted of the following laboratory strains: Staphylococcus aureus Oxford, Staphylococcus aureus WCUH29, Streptococcus pneumoniae 1629, Streptococcus pneumoniae N1387, Streptococcus pneumoniae ERY2, Enterococcus faecalis I, Eiterococcus faecalis 7, Haemophilus influenzae Q1, Haemophilus influenzae NEMC1, E. coli 7623 (AcrAB+), E. coli 120 (AcrABxe2x88x92), and Morexalla catarrhalis 1502. The minimum inhibitory concentration (MIC) was determined as the lowest concentration of compound that inhibited visible growth. A mirror reader was used to assist in determining the MIC endpoint.
One skilled in the art would consider any compound with a MIC of less than 256 xcexcg/mL to be a potential lead compound. Preferably, the compounds used in the antimicrobial assays of the present invention have a MIC value of less than 128 xcexcg/mL. Most preferably, said compounds have a MIC value of less than 64 xcexcg/mL.
The examples which follow are intended in no way to limit the scope of this invention, but are provided to illustrate how to make and use the compounds of this invention. Many other embodiments will be readily apparent to those skilled in the art.